John Belushi was meant to star: The project was originally written by Dan Aykroyd to star with his Blues Brothers co-star Belushi, who died in 1982.

Says director Ivan Reitman: "Before I was involved, Dan Aykroyd had written a treatment for a kind of extraterrestrial futuristic ghostbusting saga that he called Ghostbusters that was meant for Belushi and himself. It was really planned as their vehicle."

Reitman had worked with Bill Murray on Meatballs and Stripes, and Aykroyd wanted to know "if it was something we could re-conceive for Murray and himself."

"He sent me the treatment. I felt it had a wonderful idea in it," says Reitman. The script was redone by Harold Ramis, who would also star in the film, and Aykroyd to tell the story we see today.

Eddie Murphy was never set to star: Somehow pre-Internet rumors (continued on the Internet) claim Murphy was meant to star in Ghostbusters. Not true says Reitman. " I don't ever remember Eddie Murphy coming up in the casting process," he says. " I think this is something that happened or started after the release of the movie, after it was a big hit."

John Candy did turn down a role: Reitman had worked with Candy on his first film, Stripes, and wanted to cast the Canadian star as the accountant neighbor down the hall. But Candy had trouble grasping the concept.

"He didn't seem to get it right away. He kept saying, 'Maybe I could play him with a German accent.' And I said that he could, but it sounds kind of goofy, And he said, 'I think I should have a big German shepherd,' " Reitman recalls. "I don't think (Candy) wanted to do it. He didn't get it. So he passed on it over the phone."

Rick Moranis jumped on the part.

"(Moranis) literally called me back three hours after receiving the script, and he said, 'Please thank Candy for me for passing on this. This is the greatest,' " says Reitman laughing. "He got it right away. And he did a spectacular job."

Dan Aykroyd in a scene from 'Ghostbusters'(Photo: Sony Home Entertainment)

Aykroyd's cigarette floated: In the scene where Aykroyd comes face-to-face with a ghost, his cigarette famously comes off his lips but somehow stays put. The stars assures there was no trick used to keep the cigarette in place.

"That was a total the-gods-are-with-you comedian moment," says Aykroyd. "I had the (cigarette) there, and I did the look. And they got the shot," says Aykroyd. "No glue, no tape, no glycerin."

Killer set: The set piece depicting the Manhattan rooftop where the dramatic ghost-busting climax takes place was one of the largest sets built in Hollywood, occupying all of stage 12 of the Burbank studio lot, which is now Warner Bros. It featured a 360-degree view of the New York skyline at night.

"It was so big we used up every power source that there was on the studio lot, including using every generator we could find," says Reitman. "That was quite something to shoot. Every major filmmaker would come by just to look at it."